Planets spin. Stars spin. Galaxies spin. Why not the universe?
British radio astronomer Paul Birch says he now has evidence to suggest the cosmos as a whole is indeed rotating.
If true, this would have what Birch calls ''drastic cosmological consequences'' for theories of the nature and destiny of the universe.
Underlying most such theories is the widely held assumption that, on a sufficiently large scale, the universe has no preferred position or direction. It would appear fairly much the same from whatever point in space you happened to view it and in whatever direction you looked.
This assumption is called the cosmological principle.
Equally fundamental is an assumption called Mach's principle. This holds that the motion of a particle has meaning only in relation to the rest of the matter in the universe.
Birch says that the rotation of the universe as a whole, which his findings imply, would be incompatible with both of these ''principles.''
The University of Manchester scientist outlined his data in Nature this past summer. They concern a sampling of double radio sources - that is, objects with two sources emitting radio noise. Such objects generally have an elongated shape.
Birch measured both the orientation of these objects with respect to a standard direction and the orientation of their magnetic fields. He expected that the angles between the directions of the objects and the directions of the magnetic fields would be more or less randomly distributed around the sky. Instead, he found them to be highly organized. They are generally positive in one half of the sky and negative in the other half.
In other words, the radio sources seem to be systematically oriented. After considering various alternatives, Birch has concluded that ''such a phenomenon can only have a physical explanation on a cosmic scale; an attractive theory is that . . . the Universe is rotating.'' This would mean that the radio sources were aligned with this overall cosmic rotation.
It would be a spin rate of one complete rotation in about 63,000 billion years. That's a rather slow waltz. But it's fast enough to shake the foundations of many cosmological theories.
John Barrow of the University of Sussex has noted that the spin appears to rule out all the standard models of the cosmos in which the current expansion of the universe would eventually reverse itself, causing the universe to collapse. Instead, the spin may imply that the universe will go on expanding forever.
Cosmologists will not be especially dismayed if Birch's suggestion turns out to be true. Many have developed models of the cosmos that do not depend on Mach's principle and the cosmological principle.
Thus the discovery of the waltzing universe may be a welcome stimulus to creative thinking about the nature of the cosmos in which we live.